<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <ol id="elem">
        <li>Hello</li>
        <li>World</li>
      </ol>
      
      <script>
        let elem = document.getElementById('elem');
        function clear(elem) { 
            while (elem.firstChild) {
            elem.firstChild.remove();
        }
        
    }
       clear(elem); // 清除列表
       
      </script>
</body>
</html>